The invention relates to positioning systems and in particular to using a writeable encoder to correct position errors. The writeable encoder can be of the magnetic or optical type.
Encoders, both optical and magnetic, are used for accurate linear and rotary positioning of machine tools, computer peripherals and electro optical instruments. In most of the applications the point of position measurement does not coincide with the point where the accuracy is required. This is due mainly to restriction in mounting the encoders. As an example, when a linear encoder is used in a machine tool it is mounted below the table surface for protection. Any deviation from straightness of the ways will cause the table position to disagree with the encoder reading. Also, any distortion caused to the encoder while mounting it or due to the difference in thermal expansion between the encoder material and the machine tool will cause position errors. It is the object of this invention to write the encoder in place automatically compensating for all the above mentioned sources of error.